Caption: Dinosaur. Conceptual artwork of a ghostly dinosaur rising above the surface of the Moon. Earth is seen at lower right. This image could represent the age of dinosaurs. Between around 250 and 65 million years ago, reptiles were the dominant form of life on Earth, with large predators such as this at the top of the food chain. However, after dominating the terrestrial fauna for millions of years, the dinosaurs died out relatively rapidly. This is thought to have been due to a large asteroid colliding with Earth. This would have rapidly cooled the Earth as dust thrown up into the atmosphere by the collision would have blocked out the Sun's rays.